Optimum blade loading

Thread Starter

windy

Joined Apr 19, 2007
26
I want a system to help in the loading of a windgenerator I am working on.

My proposed design uses an additional small windturbine that will be unloaded and will be used for wind speed readings. Although the wind speed will not be calculated only compared to the speed of the loaded turbine. this is to load the turbine for optimum aerodynamics.

I am thinking a counter that is reset by the freq of the loaded turbine, when the number gets to large PWM loading would reduce the load to keep the blades from stalling, therefore getting the max power from the system.

On the opposite side of the picture to low a number would indicate a need to not load the blades so the turbine will start at lower wind speed.

I am thinking that a PIC controller may do the job, but my last use of such things were a long time ago. what I am wondering is do you know of a proto board populated and ready to go. with USB connections and onboard programming, maybe with built in PWM support. Also a supplier I could contact
 

Papabravo

Joined Feb 24, 2006
13,512
That's too bad. Variable pitch seems like an obvious solution for load management. High angle of attack at low speed and reduced angle of attack at high speed. In an airplane a variable pitch prop is used to keep engine speed constant.
 

beenthere

Joined Apr 20, 2004
15,819
Your additional small turbine might be refered to as an anemometer.

Have you looked at the work on such systems done in the 1930's? We still have some old Winchargers spinning locally. There is even a site devoted to them - http://www.wincharger.com/.
 

Thread Starter

windy

Joined Apr 19, 2007
26
yes, anemometer is what I would call it. In my case I am not after finding windspeed though. I want to use the freq difference to determine loading. I am not trying to maintain speed (freq, or voltage). I am trying for the best power crop I can get at all speeds by applying a variable load.

I will be working on increasing slip on an induction generator to the point just short of stalling the aerofoil. The turbine has a power curve of 1000w and,
I will be using a 4pole 3phs 2.2KW motor as the generator established in the conference paper published by the NREL NREL/CP-500-26713 it states in there experment that the results showed the motor could produce power at half its rated RPM. At lower voltage requirements I am thinking the motor will produce at even lower RPM, only testing will tell, because that was not there concern.

In answer to your question, I have been researching different designs for quite a while, but until I came upon "self excited" to use for my keyword search, I was looking at other self built PM generator progress. Mostly because the plan is for off grid use and didn't think I could build self excited induction generators with out many mods to the motor.
 

Thread Starter

windy

Joined Apr 19, 2007
26
I would like to bring this thread back to the question. I am wondering if anyone has a recommend as far as what PIC controller would be best suited for this application. I have found many options using the MAPS program on there web site, but would like input from people as to the units they like the best when building such a project.
 

recca02

Joined Apr 2, 2007
1,214
can the principle of governor mechanism not be used?
of course we can not change flow rate of air but may be load on turbine can be changed by the use of this method.
 

Thread Starter

windy

Joined Apr 19, 2007
26
can the principle of governor mechanism not be used?
of course we can not change flow rate of air but may be load on turbine can be changed by the use of this method.
I am not conserned about overspeed, I am conserned about underspeed resulting in stalling. I have not figured out how to regulate loading without knowing windspeed and slip. What are you thinking with governor that will overcome this need for information and need to act on it.
 

Papabravo

Joined Feb 24, 2006
13,512
The flyball governor was an early example of a servo mechanism used to regulate early steam engines. The governor was coupled to the line shaft. As the line shaft would speed up the balls would move outward causing a valve to reduce the steam pressure reducing the speed of the line shaft.

One of the cool features of this mechanical system is that the non-linear differential equation can be linearized and solved in closed form for small deviations about an equilibrium point.
 

recca02

Joined Apr 2, 2007
1,214
well, i only wanted to inquire abt the possible usage of the mech.
as can be done with steam and water turbines .
i happen to know abt those but i havent read anything abt windmills till yet.
thanks mr papabravo i was thinking abt that analogy myself.
 
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